The disclosed invention generally relates to water heater controllers, and more specifically is directed to an adaptive water heater controller which controls water heater operation as a function of actual hot water usage.
Water heater systems commonly are configured to maintain the supply of hot water at a sufficiently high temperature to meet peak hot water usage, regardless of the actual usage. It has been long recognized that substantial amounts of energy are utilized in maintaining the high water temperatures necessary to meet peak usage. During periods of low or no usage, much of that energy is wasted.
Various techniques and controllers have been developed to reduce the amount of energy loss in hot water heater systems.
An example of a simple water heater controller is time clock which turns off the water heater system during preset time periods known to have no hot water demand, for example in a school at night. However, a large temperature drop in the hot water supply would require a long period of time to bring the hot water supply up to temperature, and the large temperature changes might required increased maintenance. Moreover, in parts of the country where freezing occurs, turning off water heater systems might cause damage due to freezing.
Other controllers determine a hot water supply temperature that is based on historical data as to amount of hot water used during specified time intervals or as to the amount of time the heater is on during specified time intervals. Such controllers, however, do not respond promptly to actual usage that departs from the historical data, and thus could maintain a supply temperature that is higher than needed for the actual usage occurring, or could maintain a supply temperature that is lower than needed for the actual usage occurring. Moreover, controllers which vary delivery temperature are believed to interfere with the built-in heater controls.